Method of spooling a bi-metallic pipe

ABSTRACT

A method of spooling a marine pipeline ( 90 ) including a plurality of bi-metallic pipe sections ( 10 ) ( 66 ) onto a reel ( 60 ) including at least the steps of: (a) filling a first pipe section with a fluid ( 12 ); (b) spooling the first pipe section onto the reel; (c) filling a second pipe section with a fluid ( 78 ); (d) joining the first pipe section with the second pipe section wherein at least one of the first and second pipe sections maintains the fluid ( 12,78 ) therein; and (e) spooling the second pipe section onto the reel.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/054,600, filed Apr. 12, 2011, which is a U.S.C. §371National Phase conversion of PCT/GB2009/050899, filed Jul. 22, 2009,which claims benefit of British Application No. 0813545.1, filed Jul.24, 2008, the contents of each application being incorporated in fullherein by reference. The PCT International Application was published inthe English language.

BACKGROUND OF THE INVENTION

The present invention relates a method of spooling a marine pipeline.

Corrosion resistance pipelines for the marine or otherwise underwatertransportation or conveying of corrosive fluids such as gas or crude oilcan be provided by pipes having an internal metallic liner. Adouble-walled or bi-metallic pipe is generally composed of two metalliclayers. The outer layer is for resisting hydrostatic pressure, and/orinternal pressure depending on the water depth, whilst the internallayer prevents damage to the outer layer from the chemical compositionof the fluid being conveyed. The inner layer is sometimes also termed a“liner”. As one of its main purposes is to protect the outer layer fromcorrosion, commonly a corrosion resistant alloy (CRA) is chosen for theliner.

One form of bi-metallic pipe is a single “clad” pipe having an internalCRA layer metallurgically bonded to the outer layer, which could beformed from a carbon steel base metal.

A second form of bi-metallic pipe can be termed a ‘lined’ pipe, where aCRA liner is fixed to the outer layer such as carbon steel withoutmetallurgical bonding. An economic method of forming a lined pipe useshydraulic expansion, where the CRA liner is inserted into the outerlayer, and then both parts are expanded. During the expansion, the outerlayer undergoes an elastic deformation while the inner pipe undergoes aplastic deformation.

There are two common methods of laying underwater or marine pipelines.The ‘stove piping method’ involves assembling pipe stalks on a marinepipe-laying vessel, and then welding each one as the laying progresses.In the ‘reeled laying method’, the pipeline is assembled onshore andspooled onto a large reel, sometimes also termed a storage reel or drum,and then unwound from the reel as the pipe is being laid. Once offshore,the pipeline is unwound from the reel and is directly available forlaying because no welding is required during the offshore operation.

The reeled laying method is faster than the stove piping method, suchthat it is preferred where possible. However, the reeling processgenerates bending on the pipeline, which would cause a lined pipe towrinkle and/or to bend. Thus, there has hitherto been no actual use orcommercial application of the reeled lay method for bi-metallic pipes.

WO 2008/072970 A1 discloses a method for laying a pipeline having aninner corrosion proof metallic cladding that is closely fitted withmetallic contact to an outer pipe material. In its method, a section ofthe pipeline is reeled onto a pipe laying drum whilst an overpressure ismaintained within the section by means of a pressurised fluid. When thepipeline is motionless, the overpressure is relieved, and a furtherpipeline section is joined to the first section. A new overpressure isthen applied within the sections, and the further section is reeled ontothe pipe laying drum.

Whilst this method may assist to avoid deformation when the pipelinesections have no “mechanical movement” (which is defined in WO2008/072970 A1 as meaning reeling the pipeline onto or unwinding thepipeline from the pipe laying drum), this method requires theoverpressuring and pressure-relieving steps every time two pipe sectionsare joined. The pipe laying drum is described in WO 2008/072970 A1 astypically having installed “many” pre-fabricated sections, creatingsignificant multiplication of the overpressuring and pressure-relievingsteps required.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a simpler method ofspooling a bi-metallic pipe onto a reel.

According to a first aspect of the present invention, there is provideda method of spooling a marine pipeline comprising a plurality ofbi-metallic pipe sections onto a reel, the method comprising at leastthe steps of:

-   -   (a) filling a first pipe section with a fluid;    -   (b) spooling the first pipe section onto the reel;    -   (c) filling a second pipe section with a fluid;    -   (d) joining the first pipe section with the second pipe section        wherein at least one of the first and second pipe sections        maintains the fluid therein; and    -   (e) spooling the second pipe section onto the reel.

By maintaining the fluid in at least one of the first and second pipesections, preferably both pipe sections, during their joining, themethod of the present invention is significantly simplified allowingfaster spooling to be effected.

The composition, nature and formation of bi-metallic pipe sections areknown in the art. Each pipe section may comprise any suitable size,design and shape.

In one embodiment of the present invention, each pipe section ispre-assembled from a number of smaller pipe sections prior to use withthe present invention. Thus, the pipe sections may extend from severalmetres long up to 1 km, or be approximately 1 km long, or be greaterthan 1 km long.

The present invention relates to all forms of bi-metallic pipe sections,preferably lined pipe sections comprising a CRA liner fixed to an outerlayer.

Each pipe section may be filled with the same or a different fluid.Fluids include all suitable liquids and/or gases, preferably being ableto be pressurised. Water or water-based fluids are typical fluids thatare usable in the present invention.

Methods and apparatus for joining two pipe sections that are well knownin the art are not described herein in detail. Generally the joiningcomprises one or more welds, such as tie-in welds. The two pipe sectionsform a combined pipe section. Once a first pipe section and a secondpipe section are joined, the so-formed combined pipe section can becomea new “first pipe section” for the method of the present invention, suchthat steps (c)-(e) can be repeated by the addition of another secondpipe section, so as to join and spool one or more further second pipesections onto the reel. Typically, a reeled pipeline for subsequentlaying via the reeled lay method can be many pipe sections, and so manykilometres, long.

Each fluid may be pressurised prior to its use to fill a pipe section,such that the method of the present invention could comprisepressurising the fluid in the first pipe section prior to step (a)and/or pressurising the fluid in the second pipe section prior to step(c).

Preferably, the method comprises pressurising the fluid in the firstpipe section after step (a) and/or pressurising the fluid in the secondpipe section after step (c).

Methods of pressurising a fluid are known in the art. The fluid may bepressurised to a pressure greater than 5 bar, preferably in the range8-12 bar such as 10 bar. A maximum pressure for the fluid depends uponthe nature and dimensions of the pipe sections, such that a generalmaximum of 25 bar will generally suit most known pipe sections.

Preferably the same fluid is used in the first pipe section as thesecond pipe section, and the or each subsequent pipe section to bejoined, and more preferably the same fluid is water.

Means to retain the fluid in a pipe section may include any suitableapparatus, device or unit, and is hereinafter termed a “plug”. Plugs maybe movable or stationary, and are preferably lockable to provide fluidresistance or sealing once located at a desired location at, in, oralong the length of a pipe section. One suitable plug can be based on apig. Other (separate or attached) plugs or pigs may also be suitable toassist movement of a plug along a pipe section of pipeline.

In one embodiment of the present invention, step (a) further comprisesthe steps of:

-   -   locating a first plug at one end of the first pipe section;    -   filling the first pipe section with a fluid;    -   locating a second plug at the other end of the first pipe        section;    -   pressurising the fluid; and    -   locking the second plug to maintain the pressurised fluid in the        first pipe section.

In another embodiment of the present invention, step (c) furthercomprises the steps of:

-   -   locating a first plug at one end of the second pipe section;    -   filling the second pipe section with a fluid;    -   locating a second plug at the other end of the second pipe        section;    -   pressurising the fluid; and    -   locking the second plug to maintain the pressurised fluid in the        second pipe section.

Two or more plugs may be attached, suitably by one or more lines, toallow for combined movement. At least one plug may be attached toanother plug or pig for movement along a pipe section.

Preferably, there is an absence of fluid in the areas of the first andsecond pipe sections being joined in step (d). A plug being used at theend of a pipe section may be located near to the end of the pipe sectionto create a portion of the end of the pipe section free of fluidthereunder. Thus, locating a plug “at” an end of a pipe section includeslocating a plug “at or near” an end of a pipe section. The skilled useris aware of the portion of a pipe section end required to form a join,generally by one or more welding processes or operations, with anotherpipe section end.

Where there is an absence of fluid in the areas of the first and secondpipe sections being joined, preferably the method further comprisessubsequently filling the first and second pipe sections beneath the joinwith a fluid, preferably the same fluid in the first and/or second pipesections.

More preferably, the fluid to be located beneath the join is providedfrom the first and/or second sections by movement of one or more plugsthereacross.

In another embodiment the present invention, one or more plugs arerelocated after joining the first and second plug sections so as toalter the number of plugs in the combined pipe section and/or thedistribution of fluid in the combined pipe section.

In one embodiment of the present invention, the method of the presentinvention comprises at least the steps of:

-   -   (i) locating a plug at one end of the first pipe section;    -   (ii) filling the first pipe section with a fluid, preferably        water;    -   (iii) locating a second plug at the other end of the first pipe        section;    -   (iv) pressurising the fluid in the first pipe section;    -   (v) locking the second plug to maintain the pressurised fluid in        the first pipe section;    -   (vi) spooling the first pipe section onto the reel;    -   (vii) locating a first plug at one end of the second pipe        section;    -   (viii) filling the second pipe section with a fluid, preferably        water;    -   (ix) locating a second plug at the other end of the second pipe        section;    -   (x) pressurising the fluid in the second pipe section;    -   (xi) locking the second plug to maintain the pressurised fluid        in the second pipe section;    -   (xii) joining the first pipe section beyond its first or second        plug with the second pipe section beyond its first or second        plug to provide a join;    -   (xiii) filling the first and second pipe sections beneath the        join with a fluid, preferably water;    -   (xiv) moving at least one plug of the first pipe section across        the join;    -   (xv) moving one plug of the first pipe section to the location        of one plug of the second pipe section, and optionally        withdrawing the first and second plugs of the second pipe        section from the second pipe section;    -   (xvi) spooling the second pipe section onto the reel; and    -   (xvii) repeating steps (vii) to (xvi) with another second pipe        section.

Two or more of the above steps may occur simultaneously and/or notsequentially as listed. The action of spooling a pipe section and/or acombined or joined pipe section onto a reel, and the shape, dimensionsand/or use of a reel, are known in the art.

According to the second aspect of the present invention, there isprovided a marine pipeline comprising a plurality of joined bi-metallicpipe sections located on a reel wherein each pipe section comprises apressurised fluid, preferably water.

According to a third aspect of the present invention, there is provideda method of joining two marine pipeline bi-metallic pipe sections, eachpipe section having a fluid therein enclosed by first and second plugsat respective ends of the pipe sections, comprising at least the stepsof;

-   -   (a) connecting opposing plugs of the first and second pipe        sections;    -   (b) joining the first and second pipe sections;    -   (c) filling the first and second pipe sections beneath the join        with a fluid; and    -   (d) moving one of the connected plugs across the join.

The method of joining two marine pipeline bi-metallic pipe sections isusable with the method of spooling of marine pipeline as defined herein.Indeed, the present invention encompasses all combinations of variousembodiments or aspects of the invention described herein. It isunderstood that any and all embodiments of the present invention may betaken in conjunction with any other embodiment to describe additionalembodiments of the present invention. Furthermore, any elements of anembodiment may be combined with any and all other elements from any ofthe embodiments to describe additional embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only, and with reference to the accompanying drawings in which;

FIGS. 1( a)-(g) are diagrammatic cross-sectional views of the filling ofa first pipe section with a fluid;

FIGS. 2( a)-(f) are diagrammatic cross-sectional views of a method ofjoining the first pipe section of FIG. 1( g) with a second pipe sectionwith a fluid;

FIG. 3 shows a diagrammatic cross-sectional view of a plug at one end ofa pipe section;

FIG. 4 shows a schematic side view of a clampable pressure chamber; and

FIG. 5 shows a schematic reeled lay method.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides a method of spooling a marine pipelinecomprising of plurality of bi-metallic pipe sections onto a reel,preferably for use in a subsequent reeled lay method for laying thepipeline offshore. Because the spooling process generates bending on thepipe sections, which may cause a bi-metallic pipeline to wrinkle orbend, the present invention provides a simplified method of being ableto spool bi-metallic pipe sections onto a reel. With even a smallinternal pressure, the bending moment of a bi-metallic pipeline isacceptable with respect to the spooling process, so that wrinkling ofthe pipeline is avoided. The present invention provides a method ofspooling such a pipeline whilst maintaining an internal preferablyhydrostatic pressure in at least first and second pipe sections.

Referring to the drawings, the presence of a fluid in a pipe section ora combined pipe section is shown in the accompanying drawings bydiagonal hatching.

FIGS. 1( a)-(g) show the step of filling a first pipe section 10 with afluid such as water 12. The first pipe section 10 could be approximately1 km long, and pre-assembled from a number of smaller pipe sections

FIG. 1 (a) shows a first pipe section 10, one end of which is attachedto a pig catcher 14, and the other end of which is attached to a piglauncher 16. Various types and designs of pigs are known in the art, andpigs are generally designed and arranged to flow freely through apipeline, and to be conveyed forward along the pipeline by the pressureof fluid therein.

A first plug 18, operable with the pig catcher 14 and the pig launcher16, and optionally being or being developed from a conventional pig, isable, adapted, or otherwise temporarily attached to another pig, to movealong a pipe section or pipeline such as the first pipe section 10. Thefirst plug 18 is preferably able to isolate air from water, be movableby low hydrostatic pressure and have low friction with an inner pipewall, be lockable in position, and be able to withstand at least +25 barof pressure, as well as being suitable to tow a low drag pull line.

FIG. 3 shows an example of a suitable plug 30 comprising a lockingdevice 31, a power and remote module 32, and an eye 34 to which abuoyant tow line 36 can be attached from a winch 38.

FIG. 1 (b) shows the pig launcher 16 launching the first plug 18, towhich is attached a first line 20. The line could be formed and/or ofplastic. Preferably, the first line 20 is a buoyant line or tow linemade of, for example, polyethylene.

As a fluid such as water 12 is pumped either in or through the piglauncher 16 into the first pipe section 10, the first plug 18progressively penetrates along the inside of the first pipe section 10as shown in FIG. 1 (c). As the water 12 further pushes the first plug 18along, the first line 20 is further deployed along the first pipesection 10 as shown in FIG. 1( d).

Sufficient water 12 is pumped into the first pipe section 10 until thefirst plug 18 is located at a distal or downstream end 22 of the firstpipe section 10 as shown in FIG. 1( e), which also shows the attachmentof a second plug 24 to the free end of the first line 20 in the piglauncher 16. The second plug 24 is then located at the first or otherend of the first pipe section as shown in FIG. 1( f) to maintain thewater 12 in the first pipe section 10.

In general, the or each plug is preferably located and/or locked at alocation near to the end of a pipe section, such that there remains afinal portion 25 of each pipe section which is free from fluid.

FIGS. 1 (a)-(f) show one example of step (a) of the method of thepresent invention.

The water 12 may be provided as a pre-pressurised fluid. Alternatively,a suitable chamber such as a clampable pressure chamber 26, is installedat the downstream end of the first pipe section 10 as shown in FIG. 1(g). An example of a suitable clampable pressure chamber is shownschematically in FIG. 4, showing a clamp 40 and a plug 42 having anattached buoyant line 44, the other end of which is attached to apulling winch 46 having a power rack 48. A manhole 50 can be providedfor visual inspection. FIG. 4 also shows a lifting means 52 able tolocate and/or remove the clampable pressure chamber when required.

FIG. 1 (g) shows the attachment of the free or previously non-attachedside of the first plug 18 to a second line 28, (the second line 28optionally being the plug 42 and buoyant line 44 shown in FIG. 4). Inthis way, the first plug 18 is attached to the pulling winch 46, and thefinal portion 25 of the downstream end of the first pipe section 10,which was previously dry, can now be filled with water. Pressure can nowbe applied through the clampable pressure chamber 26 to increase thepressure of the water 12 in the first pipe section 10, optionallythrough one or more remote control valves in the first plug 18, andoptionally until there is a pressure of approximately 10 bar. The firstplug 18 can then be fully locked.

With pressurised fluid therein, the first pipe section 10 can then bespooled onto a reel (such as reel 60 shown in FIG. 5) in a manner knownin the art. Spooling of a bi-metallic pipe section having an internalhydrostatic pressure limits the bending moment of the pipe section withrespect to the spooling process, such that wrinkling is avoided.Preferably, the pressure of the fluid 12 in the first pipe section 10 ismaintained whilst the first pipe section 10, now located on a reel, isjoined to a second pipe section.

FIG. 2 (a) shows the downstream end of the first pipe section 10 havingwater 12 therein maintained by the first plug 18 (and the second plug 24not shown in FIG. 2). The free side of the first plug 18 is connected bya short third line 62 to a third plug 64 (or second ‘first plug’)located at one (upstream) end of a second pipe section 66. The secondpipe section 66 has the third plug 64 at one end thereof, and a fourthplug 68 (or second ‘second’ plug) at its other or downstream end. Thethird and fourth plugs 64, 68 are connected by a fourth line 70therebetween. The other side of the fourth plug 68 is connected to awinch 72 in a clampable pressure chamber 74 by a further line 76, whichclampable pressure chamber 74 may be the same or different to theclampable pressure chamber used in FIG. 1 (g) and/or shown in FIG. 4.

The method of:

-   -   locating the third and fourth plugs 64, 68;    -   filling the second pipe section 66 with a fluid 78, preferably        being the same fluid such as water as the first fluid 12; and    -   pressurising the second fluid 76;    -   are preferably the same or similar to the processes described        above in relation to FIGS. 1 (a)-(g).

FIG. 2 (b) shows the bringing together of the ends of the first pipesection 10 and the second pipe section 66 so as to be joined, preferablywelded using one or more tie-in-welds 80, to create a join 80 as shownin FIG. 2 (c). The first and second pipe sections 10, 66 now form acombined pipe section 82 because of the join 80. A coating may beapplied to the outer wall of the combined pipe section 82 around thejoin 80, such as a field joint coating known in the art.

FIG. 2 (d) shows a method of equalising the pressure inside the lengthof the combined pipe section 82, wherein the first, third and fourthplugs, 18, 64, 68 are unlocked or otherwise prepared for being movable,and the winch 72 is operated to cause movement of the connected first,third and fourth plugs 18, 64, 68 through the connected lines 62, 70,76. In this way, the first plug 18 is moved across the location of thejoin 80 to be present in the second pipe section 66, and the areapreviously absent of fluid in the first and second pipe sections 10, 66beneath the join 80, is now filled with the fluids 12, 78, which combineto provide a single fluid in the combined pipe section 82.

Preferably, the first plug 18 is then relocated to be at the same orsimilar position previously occupied by the fourth plug 68, such thatthe first plug 18 becomes the final downstream plug of the combined pipesection 82 as shown in FIG. 2 (e), preferably with removal of the thirdand fourth plugs 64, 68 from the combined pipe section 82. The clampablepressure chamber 74 can then be removed to leave the combined pipesection 82, with one downstream ‘end’ plug as shown in FIG. 2 (f).

The new part of the combined pipe section 82 comprising the second pipesection 66 can now be spooled onto the reel using the same process asthe spooling of the first pipe section 10. The free or downstream end 84of the combined pipe section 82 is now able to be used for joining toanother ‘second’ pipe section in a repeat of the steps and actions shownin relation to FIGS. 2 (a) to (e).

In this way, a plurality of bi-metallic pipe sections can be spooledonto a reel whilst maintaining internal hydrostatic pressure because ofthe presence of two plugs, one at each end of at least those pipesections on the reel, and two plugs at each end of each new second pipesection to be added thereto.

Variants of pressurising a fluid in a pipe section are known in the artwhich are equally useable in the present invention as long as at leastone of the first and second pipe sections maintains the fluid thereinduring the joining of such pipe sections together.

FIG. 5 schematically shows a reel 60, from which a mounted bi-metallicpipeline preferably still maintaining an internal hydrostatic pressure,may be used in the reeled lay method of laying a marine pipeline. Thereeled lay method of laying a marine pipeline is relatively quicker thanthe other main method of laying a marine pipeline, the stove pipingmethod. Thus, it is preferred for economical reasons.

During the laying process, the marine pipeline 90 is un-spooled, passedthrough one or more straightners 92 and/or one or more tensioners 94,prior to passing below a vessel 96 to be laid in a marine environment.Methods of unlocking and removing the remaining plugs in a laid marinepipeline, and for equilibrating the pressure inside the pipeline withthe environmental pressure, are known in the art. This may include theuse or more ROVs and/or pig traps.

In particular, the present invention provide a method of spooling aplurality of bi-metallic lined pipe sections onto a reel for use in asubsequent reeled lay method. This therefore combines the benefit ofusing a bi-metallic pipeline, and the economy of the reeled lay methodfor laying the pipeline in a marine environment.

Various modifications and variations to the described embodiment of theinvention will be apparent to those skilled in the art without departingfrom the scope of the invention as defined in the appended claims.Although the invention has been described in connection with a specificpreferred embodiment, it should be understood that the invention asclaimed should not be unduly limited to such specific embodiment.

What is claimed is:
 1. A method of spooling a marine pipeline comprisinga plurality of bi-metallic pipe sections onto a reel, the methodcomprising at least the steps of: (a) filling a first pipe section witha fluid and pressurising the fluid in the first pipe section; (b)spooling the first pipe section onto the reel; after this, (c) filling asecond pipe section with the same fluid and pressurising the fluid inthe second pipe section prior to joining the first and second pipesections; after this, (d) joining the first pipe section with the secondpipe section, wherein each of the first and second pipe sectionsmaintains without relieving the pressurised fluid therein; (e) spoolingthe second pipe section onto the reel.
 2. A method as claimed claim 1,wherein the bi-metallic pipe sections are lined pipe sections.
 3. Amethod as claimed in claim 1, wherein step (a) further comprises thesteps of: locating a first plug at one end of the first pipe section;filling the first pipe section with a fluid; locating a second plug atthe other end of the first pipe section; pressurising the fluid; andlocking the second plug to maintain the pressurised fluid in the firstpipe section.
 4. A method as claimed in claim 1, wherein step (c)further comprises the steps of: locating a first plug at one end of thesecond pipe section; filling the second pipe section with a fluid;locating a second plug at the other end of the second pipe section;pressurising the fluid; and locking the second plug to maintain thepressurised fluid in the second pipe section.
 5. A method as claimed inclaim 4, wherein two or more plugs are attached to provide combinedmovement.
 6. A method as claimed in claim 1, wherein the fluid ispressurised to between 5-25 bar.
 7. A method as claimed in claim 1,comprising providing an absence of pressurised fluid in the areas of thefirst and second pipe sections being joined in step (d).
 8. A method asclaimed in claim 7, comprising subsequently filling the first and secondpipe sections beneath the joint of the first and second pipe sectionswith a fluid.
 9. A method as claimed in claim 1, comprising repeatingsteps (c)-(e) to join and spool one or more further pipe sections ontothe reel.
 10. A marine pipeline comprising a plurality of joinedbi-metallic pipe sections located on a reel wherein the marine pipelineis positioned and configured to undergo the method of claim
 1. 11. Themethod of claim 1, wherein the joining comprises: (a) connectingopposing plugs of the first and second pipe sections; (b) joining thefirst and second pipe sections; (c) filling the first and second pipesections beneath the joint between the first and second pipe sectionswith a fluid; and (d) moving one of the connected plugs across thejoint.
 12. A method as claimed in claim 1, wherein the fluid is water.13. A method as claimed in claim 1, wherein the fluid is pressurised ina range 8-12 bar.